C/2021 Y1 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	12 Dec 2022	14.2	2.615 AU	1.692 AU	03h59m	+05°45'	154.5°	9.3°	45°
Perihelion	1 May 2023	13.8	2.032 AU	2.515 AU	04h43m	-24°12'	50.7°	22.6°	137°
Today	7 Aug 2026	24.8	10.738 AU	10.394 AU	16h13m	-06°40'	107.2°	5.2°	105°

The interactive orbit chart above shows the comet's path through the solar system and its position at the given date. Green and blue lines are shown perpendicular to the ecliptic plane: Green if the path is above the ecliptic plane, blue if it is below. (Left-click and drag to rotate the view; Right-click and drag to move the view; Use scroll wheel to zoom in our out.)

Light curve

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations from COBS. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.5 + 5 log[∆] + 10.9 log[r]). An additional green curve is displayed when an increase in apparent brightness is expected due to forward scattering of sunlight, which occurs when a dust-rich comet is located between the Earth and the Sun. (See Marcus 2007)

Charts

The all-sky chart below shows the path of the comet over the same period as the light curve. The comet's current position is marked yellow.

The following chart shows the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Orbital elements

The orbital elements of C/2021 Y1 (ATLAS) are:

    e (Eccentricity)                : 1.0018320
    q (Perihelion distance)         : 2.0323350
    i (Inclination)                 : 77.14920
    Ω (Longitude of ascending node) : 244.75930
    ω (Argument of perihelion)      : 245.86150
    L (Longitude of perihelion)     : 271.15522
    B (Latitude of perihelion)      : -62.83586
    T (Time of perihelion passage)  : 2460065.65620

    Epoch                           : 2026 Aug 07
    Reference                       : MPC194178

    Classification(s):              : Nearly isotropic; New (a > 10000 AU)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-08-06 00:00 UT   16 13 40.3   -06 40 06    10.354   10.726  108.9    5.1   106   24.8 
2026-08-07 00:00 UT   16 13 34.6   -06 40 08    10.377   10.733  107.9    5.2   105   24.8 
2026-08-07 18:24 UT   16 13 30.6   -06 40 10    10.394   10.738  107.2    5.2   105   24.8 
2026-08-08 00:00 UT   16 13 29.4   -06 40 11    10.399   10.739  107.0    5.2   105   24.8 
2026-08-09 00:00 UT   16 13 24.5   -06 40 16    10.421   10.746  106.0    5.2   105   24.8 
2026-08-10 00:00 UT   16 13 20.0   -06 40 21    10.444   10.753  105.1    5.2   105   24.8 
2026-08-11 00:00 UT   16 13 15.9   -06 40 29    10.466   10.759  104.1    5.2   104   24.8 
2026-08-12 00:00 UT   16 13 12.2   -06 40 37    10.489   10.766  103.2    5.3   104   24.8 
2026-08-13 00:00 UT   16 13 08.8   -06 40 47    10.512   10.773  102.3    5.3   104   24.8 
2026-08-14 00:00 UT   16 13 05.8   -06 40 58    10.534   10.780  101.3    5.3   104   24.8 
2026-08-15 00:00 UT   16 13 03.2   -06 41 11    10.557   10.786  100.4    5.3   103   24.8 
2026-08-16 00:00 UT   16 13 00.9   -06 41 24    10.580   10.793   99.4    5.3   103   24.8 
2026-08-17 00:00 UT   16 12 59.1   -06 41 39    10.603   10.800   98.5    5.3   103   24.9 

    Terminology:
            
    delta:  distance between comet and earth in AU
    radius: distance between comet and sun in AU
    magn:   magnitude (brightness) estimate    
    ra:     right ascension in hours (24h = 360deg)
    dec:    declination in degrees
    elong:  elongation in degrees (angle sun-earth-comet)    
    phase:  phase angle in degrees (angle sun-comet-earth)        
    AU:     Astronomical Unit (mean distance between earth and sun: 149597870.7 km      
    

Orbital elements usually provided by the MPC (Minor Planet Center).
Observations contributed by observers worldwide, via COBS (Comet Observation Database) or the MPC (Minor Planet Center)
Calculations by a modified version of AAPlus, a C# implementation of the AA+ project by PJ Naughter from the algorithms presented in the book "Astronomical Algorithms" by Jean Meeus.
NGC2000 dso catalog and star labels from VizieR as provided by the Strasbourg astronomical Data Center.
Tycho2 catalog from the ESO archive.